Voice-operated relay



May 1, 1923. 1,453,430

0. B. BLACKWELL VOICE OPERATED RELAY Filed Nov. 22. 1919 I NVENTORATTORNEY Patented May 1, 1923.

OTTO B. BLACKWELL, OF GARDEN CITY, NEW YORK, ASSIGNOR T0 AlVIERICANTELE-PHONE AND TELEGRAPH COlVLPANY, A CORPORATION OF NEW YORK.

VOICE-OPERATED RELAY.

Application filed. November 22, 1919. Serial No. 339,799.

To all whom it may concern Be it known that I O'rro B. BLACKWELL,residing at Garden (Jity, in the county of Nassau and State of New York,have invented certain Improvements in Voice- Operated Relays, of whichthe following is a specification.

This invention relates to transmission systems and more particularly tosuch systems which include repeaters o-r relaying arrangements for thereinforcement of the transmitted energy.

The repeating or relaying arrangements of this invention are of thevoice operated type, in which a two-way one element repeater isemployed, the proper association of the device with the circuit beingcontrolled by the voice or speech currents transmitted over the circuit.It is a general feature of this invention to provide an improvedarrangement of this character in which the voice operated relayingdevice will not be subject to interference from currents of frequenciesor characteristics other than those of the voice or speech currents andaccordingly will not be subject to false operation. Another featureconsists in an improved arrangement whereby the relay or repeater uponbeing operatively associated with the transmission line when speech isbeing transmitted thereover in one direction, will remain permanentlyassociated with the line in such manner until speech'is transmittedthereover in an opposite direction. Other and further features of theinvention will be clear from the detailed description of the inventionhereinafter given- The repeater device of this invention is operativelyconnected to the transmission line by a plurality of switches, theswitches in turn being controlled by relay means operated by the voicecurrents transmitted over the line. In order to prevent false operationof the device filtering arrangements are associated with these relaymeans. These filters are adapted to readily allow the transmission ofcurrents of telephonic or voice frequencies, but serve to attenuate andpractically extinguish currents of other frequencies. This arrangementprevents the relay means controlling the repeater device from operatingon currents of other than voice frequencies, such as currents used forsig naling or other purposes. The switches employed are of theoverbalanced type, which when thrown in one direction tend to remain inthat position until again acted upon by exterior forces.

The invention may be more fully understood from the followingdescription when taken in connection with the accompanying drawing inthe Figures 1 and 2 of which are illustrated circuit diagrams embodyinga preferred form of the invention and a modification thereof. Fig. 3illustrates a conventional type of audion amplifier.

In. the arrangements illustrated in Fig. 1 are shown two sections L andL of a trans mission line which are inter-connected through transformersl and 2 by an auxiliary circuit including the voice operated repeaterdevice. By means of these transformers the condition of unbalance in theauxiliary circuit is prevented from affecting the lines. The repeaterelement 11 is shown as of the mechanical type although other types, suchas the well known vacuum bulb repeater may equally well be employed. Theinput circuit of repeater 11 is connected to conductors 10 and 4: of theauxiliary circuit,

while the output circuit of repeater 11 is connected through transformer12 to con ductors 9 and 4 of the auxiliary circuit. The conductors 9 and10 are associated with conductors 8 and 8 of the auxiliary circuit bymeans of the switches 5 and 7, which as has been formerly pointed outare of the overbalanced type. The switches 5 and]? and also the switch 6are controlled by the polar iZed relay 22, the windings of which areclifferentially arranged. This arrangement may be termed the reversingswitch. Relay 22 is in turn controlled by the relays 19, 20, and 21. Therelay 19 responds to voice currents transmitted over the system when thetransmission is taking place from line L to line L and the relay 20 isoperative with voice currents transmitted over the system whentransmission is taking place from line L to line L Relay 20 may betermed the master switch. Associated with relays 19 and 20 are thefilters 13 and 18 respectively. These filters may be of the typeillustrated in the patents issued to Gr. A. Campbell, on hlay 22, 1917,#1227113 and 1227114, and are adapted to readily allow the transmissionof currents of voice or telephonic frequencies but which attenuate andpractically extinguish currents of other frequencies, thereby preventingrelays 19 and 20 from alue. The

' trated 5 and that t llll'lSill 1 en 0 place 'it'rorn 1111 i1 i ng n fthrough J [0 niei i switch 4, right hand (01 t (i cc through winding; oflater 11, and over conductor t th ansfornier The electro-niz this circ'torni Iron T6902... transfer in lb whence naitted over 1e 'fOllOWlterminal 0: the trensiornier minding, over conductor right hand contactof switch 5, switch conductor 8, w 1 ing of trans/o i nducu other terninel l i 12. The iin'iplifiec' Waves l initteil through the trz isformer32 over the line L A i of the cur coming 11] liroin line is. v fromconductor" I 1 3, Winding; of re ie 15, to conductor T relay 19 whichWill pu, open the following from one pole of conductor 30 9 u i nicer 'ir 13, coi'ieuctor l, s i outset o re my 19, conductor 29, to oppo polehstterv. eningz eat this circuit W :lco 1 iron conductor 9C()l'1(l1l(bOl' i' Winding: oi relay 20, co r uctor and armature ofrelay 931, c riucti 1S. conductor 17., to cl nfluctm; ins! ol tinormally ch s;

vent the tllllpliillk nitted thron trti 1 tronsn'iitted tliroi :3stir-iii rcliw 20. in

une iei tery 24, conductor 60, winding of relay 22, conductor (51,switch 6, l ft hand contact of switch 6, conductor to positive pole ofwttery and at the 811E116 time from negac pole of bat y conductor 27,contact iiri'iizrture renry 20, conductor 28, (Zing oi relay 2:2,conductor 62, switch 6, ha d contact f switch 6, conductor 25, ire poleof battery 2 1." As the two relay 2:2 diherentizilly zirover the onedcircuits will neutralize each other and the relay will not be 0;)-

tlie switches will not be thrown. 1 the switches are or the overwillremain in their after the transmission in line L to line L has I lun ision of socech new starts )in @110 other end 01' the sys- J to line Lthe voice cur- .nsrni ted from the line L tl tiens'i oriner 2 and thenceover over conductor 8, switch 5 I l c thereof conductor 9,

' Winding of relay 20, ild armature of relay or 31 filte l8 conductor17, ver "ng of transformer ot current over this y 20. The operation 2toreviously traced circondumo Accordingly the curplGVlOUSly traced cirierw nding o1 relay 22 ne position indicated in I he dotted lines. The 1 (5will also be thrown at a slight interrel after the operation of switches5 and 7 for essons which Will he pointe out later.

Upon the operation 01' switches and 7 the voice currents coming in fromline L Will transmitted over tie following circuit: winding 01%transformer 2, over 01 switch 5 and left hand contact conductor 10through Winding ol" and over conductor 4 to the 2 6 trens'l'ornier Thevoice currents ill then be transmitted in (unplified torn from therepeater 11 through transi 12 nd over the followin circuit: ron Wino o1transformer 12 conductor '1 l 9 left hand Contact 01' switch '1 switch'7, mudictor winding; oi? twinstornier l conductor 14 Winding oftransformer 1:2. The :uiiniiiied talking curre; will 'i]Y'fi.1.F;li1lQ"?(l through transformer 1 and out over line ll When the sWi ch 5 hasheeii thrown into the position indi sited by the if the talking currentdotted line a norton o i L Will he transn'iittcil coming in over lneover the following circuit: from winding of transformer 2, conductor 8,switch 5, left hand contact of switch 5, conductor 10, conductor 14,filter 13, winding of relay 19, filter'13, conductor 15, conductor 4, towinding of transformer 2. The current transmitted over this circuit willenergize relay 19, which in the same manner as previously pointed outwill deenergize relay 21, which will open the circuit of relay 20,thereby deenergizing relay 20. As has been formerly pointed out theenergization of relay 20 served to open a circuit including one of thedifferential windings of polar relay 22, thereby allowing the relay 22to be energized by current flowing from the negative pole of battery 24through the other differential winding thereof. If the switch 6 wasoperated instantaneously and thrown while relay 20 was operated currentwould now flow from the positive pole of battery 23, conductor 60,winding of relay 22, conductor 61, switch 6, right hand contact ofswitch 6, conductor 26, to negative pole of battery 23. As this currentis of the opposite .polarity it would tend to throw the switch 6 back atonce to its original position. Accordingly the switch 6 must beregulated so that by the time it has made contact with its right handcontact the relays 19 and 20 will have operated and 21 will have beenreleased, in turn releasing 20. Accordingly when the right hand contactof switch 6 is closed the current from battery 23 will be flowingthrough both of the differential windings of relay 22 and the relay willnot tend to throw the switch back to its original position. As theswitch 6 is of the overbalanced type it will tend to remain as thrownand maintain its right hand contact closed until acted upon again byexterior forces. If the direction of speech should again be reversed andtransmission should take place again from line L, to line L the voicecurrents would now be transmitted over the following circuit: fromwinding of transformer '1, conductor 3, switch 7, left hand contact ofswitch 7, conductor 16, filter 18, winding of relay 20, conductor 32,contact and armature of relay 21, conductor 31, filter 18, conductor 17,conductor 4, to winding of transformer 1. These voice currents willoperate relay 20 and open the circuit including one of the differentialwindings of relay 22. Current will now flow from positive pole ofbattery 23, over conductor 60, winding of relay 22, conductor 61, switch6, right hand contact of switch 6, conductor 26, to negative pole ofbattery 23. As has been formerly pointed out this current is of apolarity suitable to cause the operation of the polar relay 22 whichupon operating will throw the switches 5, 7 and 6. For the same reasonsas previously pointed out if the switch 6 was operated instantly andthrown while relay 20 was operated the current flowing from the negativepole of battery 24 through only one of the differential windings ofrelay 22 would tend to throw switch 6 back again to its former positionas soon as it made contact with its left hand contact. Accordingly theswitch 6 must be made to act sufficiently slow so that by the time itcloses its left hand contact the incoming voice currents will haveoperated relays 19 and 21 and thereby allowed relay 20 to be released.Accordingly when the switch 6 closes its left hand contact current willflow from the negative pole of battery 24 through both of thedifferential windings of relay 22 and? the relay will remainunenergized. Accordingly by making the switch 6 of the overbalanced typeand regulating its operation as described the relay 22 may be controlledby the opening and closing of relay 20 and theswitches 5, 7, and 6 maybe controlled by the direction of transmission of the voice currents,the switches remaining in operated position even after the transmissionof voice currents has ceased. This feature serves to prevent anydistortion of the voice currents which would otherwise result if, as informer arrangements, the switches tended to fall back in to anonoperative position upon the cessation of the voice currents.

In the arrangement illustrated in Fig. 2 is shown a modification of thearrangements of Fig. 1. Similar reference numerals have been used todenote like parts in both figures of the invention. Two sections L, andL,, of the transmission line are shown interconnected by an auxiliarycircuit, in which is included the repeater device 11. The repeaterdevice is associated with the talking conductors of the auxiliarycircuit by means of the switches 39 and 40. The switches 39 and 40 areof the overbalanced type and are controlled by the differentiallywoundpolar relay 45. The relay 45 is controlled by the direction of thevoice currents transmitted over the line through the operation of therelays 34 and 35. Associated with the relays 34 and 35 and also with therelay 38 are the filters 13, 36 and 18, respectively. These filters areadapted to readily allow the transmission of currents of telephonic or.voice frequency, but serve to attenuate and extinguish currents of allother frequencies.

The operation of the arrangement illustrated in Fig. 2 is asfollowsrWVith the switches 39 and 40 thrown in the position as indicatedin the drawing, transmission may take place from the line L to the lineL in the following manner: from the wind in of transformer 1, overconductor 3, switch 40, right hand contact of switch 40, conductor 10,winding of repeater 11 and over conductor 4 to the winding oftransformer 1. The electro-niagnetic waves transmitted over this circuitwill operate the repeater 11. The talking currents will then betransmitted in amplified form from the repeater 11, through thetransformer 12 and over the following circuit: from the winding oftransformer 12, over conductor 9, right hand contact of switch 39,switch 39, conductor 8, winding of transfori'ner 2, con ductor at to thewinding oi. transformer 12. The amplified voice currents will then betransmitted through the transformer Q'and out over the line L The voicecurrents transmitted in the above described manner from the line L tothe line L will also be transmitted from conductors 10 and 4;, throughthe filter l8 and about the winding of relay 38, thereby operating relay38. The operation of relay 38 opens a local circuit for relay 37,thereby deenergizing said relay. The deenergization oi? relay 37 al.lows its armature to retract and thereby opens the normally closedbridges across the auxiliary circuit which include the windings ofrelays 34 and 35. It is pointed out that the relays 38 and 37 areadjusted to be slightly faster in their operation than either of therelays 34- and 35, so that the voice currents transmitted from line L,to line L will cause them to operate betore the same current might causethe relays 3-1 and 35 to operate. Accordingly these two last mentionedrelays will remain unaffected by the voice currents transn'iitted fromline L to line L and the relay L5 and the switches 39 and 40 will beundisturbed.

If the direction of speech is now reversed and transmission takes placefrom the line L to the line L the cessation of the voice currents fromline L to line L will cause the relays 3S and. 37 to be released. Aportion of the voice currents coming in from line L2 will be transmittedover the following circuit: from conductor 8. over conductor 51, filter13, winding of relay 3%, filter 13, conductor 50, conductor 4L8,armature and contact of relay 3?, conductor 4-9 to conductor l. Thesevoice cur rents will not be transmitted through the relays 38 or Thesecurrents will operate relay 34 and will open a circuit includ ing one ofthe dii'lerentially arranged windings of relay 45. Current will then betransn'iittcd through the other differentially arranged winding of relay45 over the tollowing circuit: from one pole of battery 52, winding ofrelay l5, conductor 13, armature and contact of relay conductor 42 tothe other pole of battery 52, As relay is polarized the currentflowingthrough this winding thereo'l will operate relay and will causethe switches 39 and 4-0 to be thrown to the position indicatel by thedotted line. When the switches and 40 are thrown in the positionindicated by the dotted line the voice currents coming in over line 2will be transmitted over the following circuit: from the winding oftransformer 2, conductor 8, switch 39, left hand contact of switch 39,winding of repeater 11, conductor a, to the winding of transformer 2.The electromagnetic waves transmitted over this circuit will operate therepeater 11. The voice currents will then be transmitted in amplifiedform through the transformer 12 and over the follow ng circuit: from thewinding of transformer 12, conductor 9, left hand contact of switch 4L0,switch 40, conductor 3, winding of transiormer 1, conductor dto thewinding of transformer 12. The amplified voice currents will thenbetransmitted through transformer 1, out over the line L As soon theswitch 39 has been thrown to the position indicated by the dotted lineby the operation of. relay 45, the voice currents from line L will betransmitted over the following circuit: from conductor 8, switch 39,left hand contact of switch 39, conductor 10, filter l8, winding ofrelay filter 18, to conductor 4. in the same manner as previouslypointed out thiswill operate relay 38, which in turn will release relayand thus open oi the previously traced circuit through relay 3% anddeenergize relay 34. When relay 34; is deenergized the relay will remainunaffected because of the diii erential arrangement of its windings andthe switches 39 and i0 being Oi the over-balanced type will remain inthe position indicated by the dot ted line and the transmission oispeech may continue to take place from line L to line i When thetransmission of speech from line L, to line L, ceases, the switches, asthey are of the overbalanced type, will remain in the position indicatedby the dotted line. it under such conditions it is now desirable totransmit speech from line L, to line L once again, the voice currentstrans mitted from line L will be transmitted over the following circuit:from conductor 3, conductor 46, filter 36, winding of relay 35, filter36, conductor L7, conductor e8, arma ture and contact of relay 37,conductor 49, to conductor 4. This will operate relay 35. However, thesevoice currents from line L, will not be transmitted to relays 34 or 38when the switches are in the dotted position. The operation oi relay 35will open a circuit including one of the differential windings of polarrelay e5. Current will then be transmitted through the otherdifferential winding of relay 45 over the following circuit: from onepole of battery 52, winding of relay e5, conductor 44, contact andarmature of relay 3%, conductor ll, to the other pole of battery 52. Asthe relay a5 is polar ized the current flowing through this otherdifferential winding thereof will operate relay 45 and will cause theswitches. 39 and ll) to be thrown from the dotted position to theiroriginal position. Transmission may then take place from line L to lineL in the same manner as already described.

l/Vhile the invention has disclosed an arrangement of filtering devicesand voice operated relays which serve to control a telephone repeater ina line, it is understood that these filtering and relaying devices maybe utilized to control devices or apparatus other than telephonerepeaters. Accordingly while the invention has been disclosed in certainspecific arrangements which have been deemed desirable it is understoodthat it is capable of embodiment in many and widely varied forms withoutdeparting from the spirit of the invention as defined in the appendedclaims.

\Vhat is claimed is:

l. A telephone line, a repeater associated therewith, a circuit changingdevice comprising a differentially wound polarized relay and a pluralityof switches for operatively associating said repeater with said line fortransmission in either direction, said circuit changing device beingcontrolled by the direction of transmission of voice currentstransmitted over said line,

and a filter associated with said circuit changing device adapted toreadily allow the transmission of currents of voice frequencies and toattenuate and practically extinguish currents of other frequencies.

2. In a telephone system, two line sections interconnected by anauxiliary circuit, a repeater in said auxiliary circuit, a

' plurality of switches so arranged that when said switches are thrownin one direction the input circuit of said repeater will be associatedwith one of said line sections and the output circuit of said repeaterwill be associated with the other of said line sectherewith, and acircuit changing device for operatively associating said repeater; withsaid line for transmission in either direction, said circuit changingdevice comprising a plurality of switches of the over balanced type, apolarized and differentially Wound relay controlling said switches, andmeans responding in accordance to the direction of flow of the voicecurrents transmitted over said line for momentarily opening a circuitincluding one of the differentially arranged windings of-said polarrelay.

4. A telephone line, a repeater associated therewith, and a circuitchanging device for operatively associating said repeater with said linefor transmission in either direction, said circuit changing devicecomprising a plurality of switches of the overbalanced type, a polarizedand differentially wound relay controlling said switches, meansresponding to the transmission of voice currents over said line formomentarily opening and closing a circuit including one of thedifferentially arranged windings of said polar relay thereby operatingsaid relay, and means controlled by the operation of said relay forreversing the polarity of the current flowing through both of saiddifferentially arranged windings.

5. A telephone line, a repeater associated therewith, and a circuitchanging device for operatively associating said repeater with said linefor transmission in either direction, said circuit changing devicecomprising a polarized and differentially wound relay, means respondingto the transmission of voice currents over said line for momentarilyopening and closing a circuit, including one of the differentiallyarranged windings of said polar relay thereby operating said relay toassociate said repeater with said line for transmission in onedirection, and means controlled by the operation of said relay forreversing the polarity of the current flowing through both of saiddifferentially arranged windings whereby when one of said differentialwindings is again opened said polar relay will operate to associate saidrepeater with said line for transmission in the opposite direction.

6. A telephone line, a repeater associated responding to thetransmission of voice currents over said line for momentarily openingand closing a circuit including one of the windings of said relaythereby operating said relay to associate said repeater with said linefor transmission in one direction, and means controlled by the operationof said relay for reversing the polarity of the current flowing through,the windings of said relay whereby when one of said windings is againopened said relay will operate to associate said repeater with said linefor transmission in the opposite direction.

7. A telephone line, a repeater associated therewith, a circuit changingdevice for operatively associating said repeater with said line fortransmission in either direction, a differentially wound polarized relayand controlling circuits therefor whereby said circuit changing devicemay be controlled by the direction of transmission of voice currentstransmitted over said line, a filter associated with. said controllingcircuits adapted to readily allow the transmission of currents of voicefrequencies and to attciuiate and practically extinguish currents ofother tirequencies, and an amplifier associated with said controllingcircuits for regulating said voice currents.

8. The combination 01f two telephone lines, a repeater therebetween,switching means for connecting said repeater to said lines and adaptedto assume different positions, whereby the two-way transmission oil;signals is p ssible, and means responsive to voice currents forcontrolling the reversal of said repeater, said means comprising; aiziastcr switch adapted to assume two positions, in one of which saidswitching}; n eans connects said repeater for the transmission ofsignals in one direction over said lines and in the other of which saidswitching means connects said repeater for transmission in the otherdirection.

9. The combination of two telephone lines, repeater therebetween,switching means for connecting said repeater to said lines and adaptedto assume different positions, whereby the tvo-way transmission ofsignals is possible, a master switch adapted to assume two positions, inone of which said switching means connects said repeater tor thetransmission of signals in one direction over said lines and in theother of which said switching means connects said repeater fortransmission in the other direction, said switch normally assuming oneof said positions, and means responsive to voice currents to move saidswitch to the other position it incoming signals do not find said switchin the proper position.

10. The combination of two lines, means adapted to be reversiblyconnected between said lines, a reversing switch between each of saidlines and said means, and a master switch controlling; said reversingswitch, said master switch being operable under the control of voicecurrents transmitted over either line, and means whereby when saidmaster switch is operated by voice currents transmitted over one line itis rendered uncontrollable by voice currents transmitted over the otherline, the movement of said master switch from one position to anotherserving" to reverse the connection of said first mentioned means to saidlines.

11. The combination of two lines, means adapted to be reversiblyconnected between said lines, a reversing; switch between each of saidlines and said means, a master switch controlling said reversing switch,the movement of said master switch from one position to another servingto reverse the connection of said means to said lines, means er switchcontrollin nd means responsive to current impressed on said lines .roractuating said master switch, and means to subject said master switch totl control oi one line to the exclusion oi": the other.

l3. it lines, a unidirectional repeater for repeat current in bothdirections between said china means for eversibly conneetrepeater tosaid lines, a voice op ed relay tor operating said switching s, andmeans conu irising a second voicerclay for rendering said first-menlayinoperative, said repeater havinput terminals normally disconnected 1one of said lines and connected to the r of said lines. is A iirepeating system comprising two ines, repeater adapter to be connectedetwecn, said repeater having its out normally connected to one of input.normally dis- 'cg said first-mentioned clay iii-- lines. a relav foreach (it said lines, mechanically iii c dent armatures for said relays,a unidn'ec onal repeater tor transmi i' current in both direct-ionsbetween.

i whereby said relays control said repca and means whereby one of saidrelays renders the energizing circuit oi a ineffective, said repeaterhaving output terminals connected to both sides of one oi said lines inthe absence of currents to be repeated.

, ation c. two telephone lines. me as adapted to be re ersibly coirnectcd between said lines. a reversing}; switch between each of sadlines and said means, and SWltClllfifZ' means responsive to voicecurrents for controlling the rerersai of said n cans, said switchi meanscomprising: a master itch con rolling: said reversi. n, the movement ofsaid switch am one position to another serving to reverse the connectionof said means to said lines. and means to subject said .master switch tothe control of one line to the-exclusion of the other.

1?.Tl1e combinatioiii of two telephone said reversing switch,

repeater system comprising two line, switching: means inc lines, arepeater adapted to be reversibly connected between said lines, areverslng switch between each of said lines and said repeater, a masterswitch controlling said reversing switch, means responsive to voicecurrents impressed on said lines for actuating said master switch, andmeans to subject said master switch to the control of one line to theexclusion ofthe other.

18. Two line sections, a device to be connected therebetween, a relaybetween said device and each of said sections, mechanically disconnectedarmatures individual to said relays, one of said relays being adapted toestablish and both of said relays being adapted to maintain theconnection of said device to said line sections.

19. The combination of two lines, a repeater therebetween, a relayresponsive to current originating in one of said lines but initiallyunresponsive to current coming in over the other of said lines, andmeans responsive to current impressed on said other line to reverse theconnections of said repeater with respect to said lines, whereby saidinitially unresponsive relay is finally responsive to current impressedon said other line.

20. The combination of two lines, a repeater adapted to be reversiblyconnected therebetween, a plurality of relays for controlling theconnections of said repeater to said lines, one of said relays being inthe output circuit of said repeater, and means comprising a movablearmature for rendering said last mentioned relay unresponsive to currentapproaching the input side of said repeater while permitting saidlast-mentioned relay to respond to current approaching the output sideof said repeater.

21. A line, a repeater therefor, a relay in the output circuit of saidrepeater for establishing the repeater connections, a mov able contactfor connecting said relay into or out of the output circuit of saidrepeater, and means responsive to voice current impressed on said linefor controlling said contact.

22. The combination of two lines, a device adapted to be reversiblyconnected therebetween, and switching mechanism for contIOlling theconnection comprising an armature connected to one side of one of saidlines, an armature connected to one side of the other of said lines, aplurality of contacts for each armature, the contacts for each of saidarmatures being connected to the opposite sides of said device, and arelay responsive to current in each of said lines for controlling saidswitching mechanism.

23. The combination of two telephone lines, a repeater therebetween, andmeans comprising a relay device responsive to current impressed on saidlines for changing the connections of said repeater to said lines,

whereby the two-way transmission of current is provided, said relaybeing responsive to voice currents transmitted over said lines and theresponse of said relay being the same regardless of whether the currentcausing it is impressed on one of said lines or is impressed on theother of said lines.

24. A signaling system comprising two telephone lines, a repeatertherefor, a relay for controlling the relation of said repeater to saidlines, said relay being adapted to be connected to either of said lines,and means controlled by said relay for connecting the input terminals ofsaid relay to one of said lines to the exclusion'of the other inresponse to voice currents transmitted over one of said lines.

25. A signaling system comprising two lines, a repeater therefor, arelay for controlling the connections of said repeater to Y said lines,and connections whereby said relay is at times responsive to voicecurrent coming in over either of said lines, is unresponsive to outgoingcurrent, and is disconnected from one of said lines whenever said linesare not in use.

26. The combination of two lines, a repeater therebetween and normallyefiective to repeat current in one direction between said lines, andmeans comprising a relay responsive to voice'current impressed on saidlines for changing the direction in which said repeater points, if notalready pointed in the proper direction, whereby the twoway transmissionof current is provided.

27. The combination of a relay, a repeater controlled thereby, and meanswhereby the actuation of said relay renders said relay in operative.

28. A two-way repeating system comprising two lines, a repeatertherebetween, a relay adapted to point said repeater in one direction orthe other between. said lines, and means whereby the actuation of saidrelay renders said relay temporarily inoperative.

29. A two-way repeating system comprising two lines, a repeatertherebetween, a relay for controlling the relation of said repeater tosaid lines, said relay being controlled by voice currents, and meanscomprising said relay for selectively maintaining whichever one of saidtwo lines was last used as the incoming line disconnected from saidrelay until the other one of said two lines becomes the incoming line.

30. In a two-way repeating system, two lines, a repeater therebetween,and means comprising a relay device responsive to voice current in eachof said lines for disconnecting the output side of the repeater from oneof said lines in response to current flow in one of said lines. 1

31. The combination. of two lines, a relay adapted to be associated witheither of said lines, said relay being controlled by voice loo currents,and means responsive to the energization of said relay for transferringthe control of said relay from one of said lines exclusively to theother.

32. A two-way repeating system comprising two lines, a repeatertherebetween, a relay controlling the repeater connections and adaptedto be associated with either of said lines, said relay being controlledby voice currents, and means responsive to the energization of saidrelay for transferring the control of? said relay from one of said linesexclusively to the other.

83. The combination of two telephone lines, a repeater therebetween, andmeans comprising a relay device responsive to voice current impressed onsaid lines for pointing said repeater in each direction whereby thetwo-way transmission of current is provided, said relay comprising asingle pair of contacts for initiating the operations of said meanswhich result in the pointing of the repeater in each direction.

'34. A signaling system comprising two telephone lines, a repeatertherefor, and a relay solenoid responsive to voice current impressed onsaid lines and adapted to be antomatically associated with one or withthe other of said lines for controlling the relation of said repeater tosaid lines.

35. The combination of two lines, a repeater adapted to be connectedtherebetween, a relay responsive to current approaching said repeaterfor controlling the repeater connections, and means for automaticallyconnecting said relay to or disconnecting said relay from the outputcircuit of said repeater.

36. The combinationo't two lines, a repeater adapted to be reversiblyconnected therebetween and normally connected to repeat current in onedirection between said lines, and a relay responsive to alternatingsignal current approaching the repeater by way of its output circuit forreversing the repeater connections to said lines.

37. A two-way repeater system comprising two lines, a repeater adaptedto be reversibly connected thereto, and means, comprising a relay coil,for reversing the repeater connections in response to energization ofsaid coil by voice current approaching the repeater in either direction.

38. A repeater system comprising two lines, a repeater therebetween, andmeans,

comprising a relay coil, for controlling said repeater in response toenergization of said coil by incoming voice current in each of saidlines.

39. A two-way repeater system comprising two lines, a unilateralrepeater adapted to be reversibly connected thereto, and means,comprising a relay coil, for reversing the pointing of said repeater inresponse to energization of said relay coil by voice current approachingthe repeater in either direction.

In testimony whereof, I have signed my name to this specification thistwenty-first day of November 1919.

OTTO B. BLAOKWELL. I

